Environmental

Producing fish feed from vegetable waste

Australians love fish and seafood! Consumption almost doubled between 1975 and 2010 and is likely to continue to grow.

Increased aquaculture is needed to meet this demand.

Most aquaculture species are still fed on fishmeal made from wild caught fish. This is both unsustainable and expensive; fishmeal prices rose steeply as fish stocks declined and demand increased.

While not economically viable in Australia at the time of this study, there is an opportunity for the vegetable industry to be involved in the development and commercialisation of fish feed produced from vegetable waste by black soldier fly larvae.

Why study this?

This project examined the use of vegetable wastes to grow insect larvae, particularly black soldier fly (BSF) larvae, which can be used in aquaculture feeds to reduce reliance on unsustainable use of wild-caught fish as feedstock.

What was done

A series of small trials examined how easily BSF can be reared in captivity, what vegetables they can eat, and how the quality of dried larvae compares to commercial fishmeal.

What we found

BSF larvae could live on a wide variety of vegetables, with feed conversion rates of around 3.3:1. As vegetables are >85% water, around 25g fresh pumpkin or 30g fresh carrot would produce 1g dried larval meal.
Adding a small amount of ground flax seed to the diet raised the larval omega-3 fatty acid content from 3 to 64 g per kg dry matter. It also significantly increased the rate at which larvae gained weight, and their feed use efficiency.

Where to next?

While results were promising, more research is needed before commercialisation. BSF would currently be an economically risky option for an individual vegetable grower.

As the price of wild caught fishmeal continues to rise, using vegetable waste to grow BSF for fishmeal could become more viable.